Research On The Fluidized Discharging Characteristics Of Kaolin Powderadsorbent And The Technology Of Entering The Furnace

During the combustion of coal,municipal solid waste and other fuels,as the temperature in the combustion boiler rises,some of the heavy metal elements in the fuel will be discharged into the environment along with the flue gas,which affects health adversely.The kaolin powder can adsorb heavy metal harmful substances,transporting it into the combustion boiler when it is working is expected to significantly reduce the heavy metal content in the flue gas of the combustion boiler.Pneumatic conveying technology for powder materials had already been widely used in fields such as powdered coal gasification,petroleum industry,pharmaceutical granulation.It was also applicable in conveying kaolin powder into combustion boiler.Discharging blow tank have advantages such as higher conveying solid-gas ratio,simpler structure,requiring easier maintenance,etc.It has important application prospects in the process of pneumatic conveying kaolin powder into the furnace.This paper proposes a revolutionary way adopting pulsed gas to break agglomeration of powder materials.A new type of top discharging blow tank was established in conveying cohesive powder.Meanwhile we studied the discharging characteristics of kaolin powder using this new type of top discharging blow tank.The results show that The introduction of the pulsed gas could effectively eliminate agglomerates,which improved the stabilities of the kaolin powders discharging.At the same time,the mechanism of granules agglomeration breaking by pulsed gas is discussed,basing on granular mechanics theory.We further studied the influence of different pulsed gas parameters（pulsed gas flow rate,pulsed width,and pulsed interval）on feeding quantity.The mass flow rate and solid-gas ratio ranged 12.6kg/h-278.04kg/h and0.9-19.56kg/m³.With the increase of fluidization gas flow rate,the mass flow rate of powders increased first and then decreased.Pulsed gas is consisited by three characteristic parameters:pulsed gas velocity(v_pulsed),pulsed interval(t_pulsed)and pulsed width(τ_pulsed).The results indicated that the mass flow rate of powders first increase and then decrease with the increase of the pulsed gas flow rate.The increase in the pulsed interval leaded to the decrease of the mass flow rate of powders.Moreover,the increase in the pulsed width leads to the initial increase and then the stabilization of the mass flow rate of powders.In addition,the study also showed that the introduction of pulsed gas changes the pressure distribution in the tank.At the same time,the mechanism of granules agglomeration breaking by pulsed gas is discussed,basing on granular mechanics theory.Meanwhile,in order to develop the process of spraying kaolin at the target temperature zone and investigate the dispersion of kaolin powder into the furnace,a numerical simulation of a 360MW"W"flame power station boiler was carried out.Based on the numerical calculation of the temperature field in the furnace,the appropriate position of the kaolin injection into the furnace was obtained,and the different gas velocity（v=20-100m/s）and gas temperature（T=900-1100K）were studied.When the conveying gas temperature T=1100K and the kaolin powders velocity v=20m/s,the distance of particle spray was short.Comparing with the middle boiler,the moving track of kaolin powders mainly focus near the boiler wall,so the dispersion of kaolin was poor.When the kaolin powders velocity v=80m/s,the distance of particle spray increased and the particles could reach the center of the boiler.In addition,kaolin particles had a larger dispersion range in the upper part of the boiler and the end of the flue,which means the dispersion of kaolin powder was better.When the kaolin powders velocity v=100m/s,the distance of particle spray increased.The particle dispersion concentration changes little.When the conveying gas velocity v=20m/s,comparing the different conveying gas temperature conditions of T=900K and T=1100K,the study show that the temperature field and flow field in the furnace are less affected under the different conditions.Therefore,the inlet gas velocity v=80m/s and inlet temperature T=900K is the better conditions for kaolin entering the furnace.